In certain applications, especially in vehicle exhaust systems, it is desired to provide a pipe joint with a high pull apart strength and a good fluid seal between the pipes. This has been provided by a wide band clamp of the type in which the band is stretched over a butt joint with tight engagement against both pipes. This pipe coupling is disclosed in the Cassel U.S. Pat. No. 3,905,623 granted Sept. 16, 1975. This patent also dislcoses a lap joint in which the outer pipe serves as a clamping sleeve and receives the end of the other pipe in overlapping relationship. Force applying means are provided on the clamping sleeve to stretch the sleeve into tight engagement with the inner pipe.
A pipe coupling with a lap joint for exhaust systems with high pull-apart strength and good fluid sealing is also disclosed in the Cassel U.S. Pat. No. 4,056,273 granted Nov. 1, 1977. The coupling disclosed in this patent comprises a wide band clamp with a sealing ring disposed around the inner pipe and having an outer diameter about the same as that of the outer pipe. the wide band clamp covers the sealing ring and the end of the outer pipe, spanning the junction therebetween, and is stretched into tight engagement against the sealing ring and the outer pipe.
Another pipe coupling for lap joints with high pull-apart strength and good fluid sealing is disclosed in Cassel U.S. Pat. No. 4,312,527 granted Jan. 26, 1982. The coupling disclosed in this patent comprises an open sleeve which is stretched around the pipes. The open sleeve comprises a roundish sector and a channel-shaped sector comprising a pair of sidewalls extending radially outwardly from the roundish sector. Force applying means are connected with the sidewalls to draw them together so that the roundish sector of the sleeve is stretched over the pipes.
In certain applications in vehicle exhaust systems, it is desired to provide a pipe coupling of the lap type in which a fluid tight seal is provided with a clamping sleeve or band which engages the outer pipe only, i.e. which does not span the outer pipe and inner pipe. In such a pipe lap joint, the fluid seal is achieved by using an outer pipe with a collapsible sealing ring or zone at its free end which is collapsed into sealing engagement with the inner pipe by tightening a clamping band thereon. A pipe lap joint of this type is disclosed in the Wagner et al U.S. Pat. No. 4,113,289 granted Sept. 12, 1978.
The collapsible sealing zone in the Wagner et al patent comprises several sets of slots which are disposed circumferentially around the end of the outer pipe. In each set of slots, there is an open slot which extends inwardly from the end of the pipe and an adjacent closed slot, i.e. it does not extend to the end of the pipe. One difficulty with this sealing zone is that the slot structure exhibits a relatively high resistance to collapsing and accommodates a relatively small amount of reduction in the circumference of the pipe at each set of slots. A lap joint of the type using a collapsible sealing zone is also disclosed in the aformentioned Cassel U.S. Pat. No. 4,056,273 wherein a collapsible sealing ring forms an extension of the outer pipe but is separate therefrom. This sealing ring is split so as to form a tongue on each free end with the tongues having complementary ramp surfaces in engagement with each other and which slide relative to each other when the ring is contracted or collapsed. This sealing ring provides a good seal but the structure is not adapted to a sealing ring which is integral with the pipe end. One difficulty is that it requires a shearing operation which results in bending in the region of the shear line and then requires reforming the pipe end.
A general object of this invention is to overcome certain disadvantages of the prior art and to provide an improved pipe lap joint.